Abstract THEMIS associates with a growing number of inflammatory diseases in humans, including Celiac Disease, Multiple Sclerosis and Atopic Dermatitis. THEMIS associated disorders affect different anatomical sites and follow different pathogeneses, placing THEMIS as one of the core ?inflammatory?-controllers. Despite the strong association of THEMIS with multiple inflammatory diseases in humans and the profound defects in T cell development and selection in THEMIS-deficient mice, the function of THEMIS and the pathways or factors it interacts with remain enigmatic. THEMIS1 is expressed in T cells where it functions as a key adaptor downstream of the TCR. In thymocytes it is essential for positive selection leading to the generation of nave T cells. THEMIS continues to be expressed in mature CD8ab and CD4 TCRab T cells but its role in mature T cells is not known. Moreover, THEMIS is expressed in the nucleus as well as in the cytoplasm and although THEMIS, as a TCR adaptor, has been well studied, it?s role in the nucleus remains undefined and nothing is known about the significance of this differential subcellular localization for its function in thymocytes or mature T cells. These significant gaps in our understanding of the biology of THEMIS greatly impede on the progress to identify the role of THEMIS in those diseases it is associated with or to design effective strategies to target THEMIS for the treatment of inflammatory diseases or to enhance protection against infections and cancers. The proposal here sets out to address these significant gaps with the use of unique new tools to examine THEMIS in the cytoplasm and nucleus of immature and mature T cells.